Reduce to simplest form. $-\dfrac{1}{4}-\left(-\dfrac{3}{5}\right)=$
Solution: $=-{\dfrac{1\cdot 5}{4\cdot5}} +{\dfrac{3\cdot4}{5\cdot4}}$ $=-{\dfrac{5}{20}}+{\dfrac{12}{20}}$ $=\dfrac{7}{20}$